1. Field of Invention
The teaching presented herein relates to a method and apparatus for determining the alignment of vehicle wheels. More specifically, the teaching relates to a method and apparatus for determining the alignment of vehicle wheels using a three-dimensional target.
2. Discussion of Related Art
It is commonly known that if the wheels of a vehicle are out of alignment with each other, it can result in excessive or uneven wear of the tires and/or adversely affect the handling and stability of the vehicle. Therefore, the wheels of a vehicle need to be periodically checked to determine whether they are in alignment. Conventionally, to determine the alignment of wheels, a two-dimensional target is mounted onto the wheel to facilitate wheel alignment. A conventional two-dimensional target 100 is shown in FIG. 1 (PRIOR ART). The illustrated two-dimensional target 100 is a planar object 105 having a plurality of target elements 120 spatially arranged in a known pattern on the object surface 110. The target elements 120 may be made retro-reflective and the object surface 110 may be non-reflective to provide suitable contrast.
The two-dimensional target 100 can be used to facilitate wheel alignment, which is disclosed in U.S. Pat. Nos. 5,535,522 and 5,809,658. A wheel alignment system (as illustrated in FIG. 9 of U.S. Pat. No. 5,809,658) may be deployed in which a camera may be set up to capture a two-dimensional image of the two-dimensional target 100, in which the target elements 120 on the two-dimensional target 100 are visible. Certain features relating to the target elements may be computed by processing the captured two-dimensional image and such features can be used to determine the alignment of the wheel to which the two-dimensional target is attached using techniques well know in the wheel alignment art.
One problem associated with use of a two-dimensional target for wheel alignment is that a two-dimensional target of a large size is needed in order to achieve accurate wheel alignment determination.